An outboard motor having an engine unit is provided with an electronic control unit for controlling the engine unit.
As one of such types of technologies, there is known an engine control unit (ECU) arranged on a front face of a cylinder block of an engine body.
Desirably, the electronic control unit is arranged around the engine unit, which is a control target, for efficient wiring.
Meanwhile, the engine unit of the outboard motor may be covered by an engine cover. When the electronic control unit is arranged around the engine unit, it is necessary to improve cooling efficiency of the electronic control unit.
In a ship, fuel stored in a fuel tank of a ship hull is pumped up to a subsidiary fuel tank, called a vapor separator, mounted in the outboard motor. The vapor separator stores the fuel supplied from the fuel tank and separates the vapor or air from the liquid fuel. The fuel stored in the vapor separator is pressurized by a high-pressure fuel pump, is supplied to an injector, and is then injected from an injector.
As one of such types of technologies, there is discussed in Patent Literature 2, a vertical-shaft vee engine unit having a vapor separator arranged in a lateral side of a crankcase and embedded with a secondary high-pressure pump. In addition, in Patent Literature 3, there is discussed a vertical-shaft vee engine unit having a vapor separator tank arranged close to a front end of a crankcase.
However, since heat is emitted to the surroundings from the crankcase and the like, the surroundings of the crankcase have a relatively high temperature. For this reason, if a vapor separator is arranged around the crankcase, the vapor separator is affected by the heat, and a temperature increases, so that a fuel vapor amount may increase unexpectedly.
Since the fuel stored in the vapor separator is pressurized by a high-pressure fuel pump and is supplied to the injector, it is necessary to arrange a fuel pipe capable of enduring a high pressure in the downstream side of the high-pressure fuel pump relatively to a fuel pipe in the upstream side. For example, as discussed in Patent Literature 1, if a vapor separator embedded with a secondary high-pressure pump is arranged in a lateral side of the crankcase, it is necessary to build a fuel pipe capable of enduring a high pressure to the injector arranged in the vicinity of the cylinder head. Therefore, the length of the high-pressure fuel pipe increases. Since the high-pressure fuel pipe is expensive more than the low-pressure fuel pipe, cost increases accordingly.